A fifty-five amino acid fragment has been prepared from the amino terminal of beta s globin. This fragment was used to immunize sheep which produced antiserum specific for the fragment. This antiserum also binds to hemoglobin S. A radioimmunoassay has been developed for measuring the interactions between the antibodies, the fragment, and hemoglobin S. This assay is being adapted to study the immunochemistry of hemoglobin S and the isolated fragment. The assay can be extended to a study of conformational changes of hemoglobin S in solution. The antibodies are being tractionated for use as immunochemical reagents in diagnosis and screening.